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January 9, 2016

MolDX Alert: Coding and Billing for Gastrointestinal Pathogen Panels (GPPs) to detect Food-Borne Infections (CM00100)

Diagnostic testing practices for enteric or food-borne pathogens (FBPs) are rapidly moving away from culture-based methods. The diagnosis of infectious diarrhea has historically been made using a combination of microscopy, culture, antigen tests, and real-time PCR. These methods have good performance but are labor intensive, time consuming and require health providers to select the appropriate tests.

Recently, GPPs, also known as culture-independent diagnostic tests (CIDTs), have been developed for the detection and identification of infectious diseases, including pathogens responsible for causing diarrhea. The Center for Disease Control and Prevention (CDC) recently published the incidence of confirmed infections per 100,000 population: Salmonella 15.9%, Campylobacter 13%, Shigella 5.5%, Cryptosporidium 3.3%, Shiga toxin–producing Escherichia coli (STEC) non-O157 1.6%, STEC O157 (0.95%). The incidence of Vibrio, Yersinia, Listeria and Cyclospora are all each less than 0.5%.

Most recently, several multiplex molecular assays have been developed for detection of FBPs. These syndromic GPPs allow health care providers to cast a broad net and achieve a timely diagnosis, but do not produce the isolates needed to distinguish between strains and subtypes for public health surveillance data and disease prevention effects. Some GPPs allow random access, while others are an "all or nothing" panel including organisms that are not reasonable and necessary for all patient populations such as children less than 5 years of age, immunosuppressed, hospitalized and community-acquired patients.

Three commercial multiplex panels (xTag GPP (Luminex); FilmArray GI panel (BioFire Diagnostics); Verigene EP (Nanosphere)) have been cleared by the FDA for the detection of GI pathogens from clinical stool samples. The Luminex xTag panel targets 14 analytes: bacteria (n=6), bacterial toxins (n=2), viruses (n=3) and parasites (n=3). The FilmArray panel targets 22 analytes: bacteria (n=11), bacterial toxins (n=2), viruses (n=5) and parasites (n=4). Verigene's EP panel targets 9 analytes: bacteria (n=5), bacterial toxins (n=2), and viruses (n=2). An advantage to GPPs panels is same-day result availability. However, the sensitivity, specificity, PPV and NPV of these GPPs vary by test type, manufacturer and other factors, and have not been reported in large groups of patients for many of the microorganisms.

Medicare is alerting providers that a "broad net" or "one size fits all" testing approach for FBPs (specifically, CPT codes 87506 and 87507) is screening and not a Medicare benefit. "One size fits all" panels contributes to test over-utilization, and increased cost to healthcare without specific benefit to a given patient. Testing should be limited to organisms with the greatest likelihood of occurrence in a given patient population, and if results are negative, with reflexive testing to more exotic organisms

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